1. Field of the Invention
The invention relates to a control system for a vehicle including a stepless speed change mechanism and a power transmission mechanism provided in parallel on a power transmission pathway between a driving power source and drive wheels.
2. Description of Related Art
One type of vehicle is well known which includes a stepless speed change mechanism, a power transmission mechanism in which one gear position or two or more gear positions is/are formed, an input rotary member to which power of a driving power source is transmitted, and an output rotary member that delivers the power to drive wheels. In the vehicle, the stepless speed change mechanism and the power transmission mechanism are provided in parallel with each other on the power transmission pathway between the input rotary member and the output rotary member. One example of this type of vehicle is described in Japanese Patent Application Publication No. 2007-278475 (JP 2007-278475 A). In a transmission of the vehicle disclosed in JP 2007-278475 A, a stepless speed change mechanism and a stepped speed change mechanism having a LOW fixed-ratio position and an overdrive fixed-ratio position are arranged in parallel with each other, between an input rotary member and an output rotary member. When the vehicle is started, power is transmitted through the stepped speed change mechanism placed in the LOW fixed-ratio position. As the vehicle speed increases to some extent, power is transmitted through the stepless speed change mechanism, in place of the stepped speed change mechanism. When the vehicle speed further increases, power is transmitted through the stepped speed change mechanism placed in the overdrive fixed-ratio position. These manners of transmitting power via the transmission are also described in JP 2007-278475 A.